Firearms such as rifles are popular among hunters, gun enthusiasts, sharpshooters, military and police personnel, and the like. Increasingly, firearm enthusiasts have favored a variety of lower receivers having incorporated designs such as the design incorporated into U.S. Pat. D773,586 for a firearm having skull design. While such novel designs are attractive and desirable, each such design is integrally formed in the lower receiver itself, limiting a single lower receiver to a single aesthetic design. A readily tailorable lower receiver is not presently available.